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TUNNEL BORING

MACHINE

INTRODUCTION

A tunnel boring machine ( TBM ) also known as a "mole", They can bore through hard rock, sand and almost anything in between. Tunnel construction by means of TBM (Tunnel Boring Machine) has become a preferred method of construction nowadays. In addition, this is well accepted by the environmentalist and the green groups. This state-of- art technology limits all works underground in building the tunnel to keep the disturbance to land, wildlife and mankind activities at ground level to a minimum throughout the period of construction. Tunnel construction by TBM is quite different from the traditional Drill and Blast Method.

INTRODUCTION

Tunnel Boring Machines are specially

designed machinery to build tunnels with a

circular cross section. Tunnels boring

machines can “dig” though a variety of soil

types including hard rock. Although these

machines can be used and are used in any

type of tunnel construction they are mostly

needed when doing Urban Tunneling, that is

when building an underground tunnel

beneath a city.TBM diameter is around

16meter and the TBM length is 7170m and

weighs about 284 tons.

MAJOR PARTS OF TBM

7  Cutter Disk : To execute rock or soft ground by the rotation of an assembly of teeth or cutting wheels under pressure against rock face.  Shield Skin : To keep the soil from getting into the machine and to provide a safe space for the workers.  Pushing Jack : To be in full contact with the erected segment and extend by hydraulic jack as the cutter turns & thrust forward.  Main Drive : To provide a force in rotating the cutter disc and is powered by electricity  Screw Conveyor : To move the soil at the cutter disc and feed onto a conveyor system.  Erector : To erect the segments to from a complete the tail of the TBM.  Back Up Facilities : To travel with the TBM & to service the operation of annular of ventilation, power & track etc.

TYPES OF TBM

They are of two types

1. Hard Rock TBM

2. Soft Ground TBM

HARD ROCK TBM

In hard rock, either shielded or open-type

TBMs can be used. All types of hard rock TBMs

excavate rock using disc cutters mounted in

the cutter head. The disc cutters create

compressive stress fractures in the rock,

causing it to chip away from the rock in front

of the machine, called the tunnel face. The

excavated rock, known as muck, is transferred

through openings in the cutter head to a belt

conveyor, where it runs through the machine

to a system of conveyors or muck cars for

removal from the tunnel.

WORKING OF TBM

Hydraulic jacks holding a TBM in place.

14

The TBM moved forward as it excavated

the tunnel by extending the pushing jacks at

the back. When the advancement of the

machine reached distance of the length of a

ring, the excavation stopped and the pushing

jacks were retrieved, a concert circular ring

in form of a numbers of segments were then

put together at the tail of the shield. The

pushing arms were once again extended in

full contact with the concert ring just erected

and excavation resumed. The cycle of

excavation and ring erection repeated as the

TBM advanced to form the lining of the

tunnel (Figure2).

The disc cutters create compressive stress fractures in the rock, causing it to chip away from the rock in front of the machine, called the tunnel face. The excavated rock, known as muck, is transferred through openings in the cutter head to a belt conveyor, where it runs through the machine to a system of conveyors or muck cars for removal from the tunnel. Boring machines are used in many applications. Examples include pile top drilling, doweling, and concentric reboring of holes on dozers, backhoes, and end loaders.  (^) Boring machines adhere to International Standards Organization (ISO) standards.

ADVANTAGE

It overcomes all the problem caused due to

Drill and Burst Method.

It can drill in kilometer

Reduction of risk of damage and accidents

It doesn't make noise pollution because it is

underground



It is eco friendly

CONCLUSIONS

The invention of the tunneling machine has

revolutionized tunneling history indeed it

had revolutionized the creation of spaces under

our cities allowing metro systems, water and

sewage systems, and underground cable

networks, all to be built in a safe and

sustainable manner.

TBMs are very varied and their suitability for

different soil conditions means that the correct

choice of machine and the level of experience

of the operators is critical in their successful

use.

Commercial considerations and pressures on

the different parties involved in the choice of

machine may affect the risk levels an

underwriter may face.

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